Serotypes of serious, sometimes fatal, streptococcal infections in Sweden during 1988-1989 were analyzed. The T1M1 type totally dominated, representing almost 70% of all group A streptococci from serious and uncomplicated infections at the peak of the outbreak. Immunoblots of isolates from various patient groups showed that all isolates produced high amounts of erythrogenic toxin (ET) B and high amounts of ET-C, whereas ET-A was released only in small amounts and from few isolates. ELISAs showed high antibody levels to these toxins and to the M1 antigen in patients with uncomplicated infections. Low antibody levels against M1 were seen in patients with bacteremia and in fatal cases; the latter also had low antibody levels against ET-B. It seems likely that a combination of production of large amounts of toxin and low antibody titers to it and to the M antigen of the infecting isolate are determining factors for the outcome of the infection. No signs of primary immune deficiency were noted.

Genetic diversity was found at high frequency downstream of the emm1 gene among T1M1 group A streptococci (GAS) isolated in Scandinavia during a recent epidemic. Clonal variation was also seen in the speA and speB genes but at much lower frequency; no variation was detected in the speC gene. Erythrogenic toxin A was found to be expressed at low levels in all strains; erythrogenic toxins B and C were produced in high amounts. All strains were found to harbor the speA, speB, and speC genes, regardless of the amount of toxin produced. No correlation was found between one specific T1M1 clone and the more serious infections when isolates from bacteremic patients (fatalities or survivors), those with uncomplicated infections, and healthy carriers were compared. Similar results were obtained in a family study in which 3 family members were found to be asymptomatic carriers of the same GAS T1M1 clone as in the bacteremic patient, defined by genotypic and phenotypic experiments.

Group A streptococcal isolates (n = 53) recovered from 38 erysipelas patients in 1988 and 1990 in Sweden were analysed with respect to serotype, erythrogenic toxin production and polymorphism in the emm gene region. Serotype determination showed a dominance of type T1M1 (28.6% of the strains), but T type 8 was also prevalent (14.3%). In the majority of the strains only a low production of erythrogenic toxin A was demonstrated, while both toxin B and C production were high. Polymorphism was detected in the emm gene region of T1M1 strains at a frequency of 64%. These erysipelas associated group A streptococci were more heterogenic with respect to serotype distribution and polymorphism in the emm gene region compared to previously studied group A streptococci isolated during an outbreak of serious streptococcal infections in Sweden in 1988/1989. The material included isolates from two cases of recurrence, and typing of the isolates indicated that the patients had been infected by the same serotype as in the primary infection.

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